Conventionally, vibrating devices using various vibration modes are used, for example, as resonators. Such a vibrating device requires a vibration plate to be supported in such a manner so as to not disturb vibration of the vibration plate.
In Patent Document 1 (identified below), a T-shaped support member is connected to a vibration member that vibrates in a longitudinal mode at the center of a surface of the vibration member extending in the length direction. The T-shaped support member includes a first portion extending in a first direction and a second portion that is connected to the first portion at the center of a side surface of the first portion and extends in a second direction perpendicular to the first direction. An end of the second portion is connected to the vibration member. The side surface of the first portion opposite the side surface connected to the second portion faces a slit formed in a base. The slit extends in the direction in which the first portion extends.
In the T-shaped support member, vibrations that have propagated from the second portion cause flexural vibrations of part of the first portion facing the slit. The part of the first portion that produces flexural vibrations serves as a vibration-reflecting portion. The length of the vibration-reflecting portion, that is, the length in the first direction, is a quarter of the wave length λ of main vibrations propagating from the vibration member.
In Patent Document 2 (identified below), support members are connected to a vibration member at the center of surfaces of the vibration member in the length direction. A support frame disposed so as to surround the vibration member is connected to the support members. Patent Document 2 discloses that a T-shaped support member enables leaks of vibrations to be suppressed.
In a structure disclosed in Non Patent Document 1 (identified below), pairs of support members are connected to nodes of a vibration plate that vibrates at a harmonic of a contour vibration. Non Patent Document 1 discloses that pairing the support members enables a spurious mode near the support members to be suppressed and enables the Q factor of main vibrations to be improved.    Patent Document 1: WO2010/110918.    Patent Document 2: Japanese Unexamined Patent Application Publication No. 10-117120.    Non Patent Document 1: “TOWARD ULTIMATE PERFORMANCE IN GHZ MEMS RESONATORS: LOW IMPEDANCE AND HIGH Q” B. P. Harrington, M. Shahmohammadi and R. Abdolvand Oklahoma State University, Tulsa, Okla., USA.
In a vibrating device disclosed in Patent Document 1, the length of the vibration-reflecting portion is λ/4. Accordingly, vibrations cannot be confined and are likely to leak to the base side.
The area of held portions joined to both ends of the first portion of the T-shaped support member is small. Accordingly, a difference in acoustic impedance between a T-shaped support arm and the held portions is small, and an acoustic reflection effect is not sufficient.
In a vibrating device disclosed in Patent Document 2, the relation between the shape and dimension of the support members and the wave length of vibrations excited at the vibration plate is not taken into account. Accordingly, leaks of the vibrations cannot be sufficiently suppressed.
In a vibrating device disclosed in Non Patent Document 1, the main vibrations may damp because of firm fixation to the support members. Accordingly, vibration characteristics are not sufficient.